The present invention relates generally to fluid spray nozzles and, more particularly, to multi-fluid component spray nozzles for use in low pressure, airless nozzle fiberglass spraying systems with external resin catalyst mixing.
Fiberglass spraying devices, and particularly hand held units, have previously employed a number of different spraying methods in attempts to provide well mixed, properly shaped fluid and spray flows in the most efficient manner possible. Typical fiberglass spraying apparatus supply fluid resin and fluid catalyst to a nozzle for internal or external mixtures. With internal mixing, catalyst fluid may typically first be atomized by mixing with air and then directed into the path of the fluid resin at the nozzle interior. After resin-catalyst mixing, the resulting fluid is forced through a common nozzle and directed at the work piece. Internal mixing requires time consuming and expensive cleaning of the nozzle and mix chambers after each use. With external mixing, both catalyst and resin fluid streams may typically be forced through separate spray nozzles prior to mixing. These nozzles are directed such that the catalyst and resin spray flows intersect to permit mixing prior to contact with the work piece. If the resin is not atomized prior to spraying, the process is often termed "airless". Such external mix sprayers may not need extensive cleaning after each use, but typically require high fluid pressures. Reinforcing fibers may typically be directed into the mixed spray path of either internal or external mix sprayers to be wetted thereby and carried to the work piece.
Major concerns in designing and operating fiberglass sprayers include providing a thoroughly mixed spray, to assure proper curing and work piece uniformity, as well as larger transfer efficiencies and lower operating costs. The term "transfer efficiencies" refers to the amount of material applied and adhering to the work product compared with the amount of waste material left in the atmosphere or elsewhere, such as the floor of the production room. Since fiberglass resin and catalyst materials are expensive and catalyst and spray mixture fumes present serious health hazards for production personnel, it is desirable to achieve as high a transfer efficiency as possible. Operating costs may be reduced by, for example, decreasing the amount of down time for system maintenance, repair, or cleaning and lowering the pumping pressure capacity needed. Further, if the spray flow fan is properly configured, production time itself may be reduced.
In prior fiberglass sprayers, the spray mixture flow stream, upon contact with the work piece or target, has generally had an oval cross-sectional configuration, taken through the logitudinal axis or axes of flow stream travel. Often, separation or "tails" from that oval shape have occured along the narrower sides. It is extremely desirable to have this cross-sectional flow configuration be as linear as possible, i.e., to have the major axis of the flow stream be many times greater than the minor axis, and to maintain uniformity of these dimensions along those axes to avoid discontinuities and tails. To the extent that such conditions are met, fabrication and spraying time, health injuries and material losses can be reduced, and fluid pump efficiency can be improved. In attempts to achieve the desired spray configuration, prior fiberglass sprayers have provided oval and V jet nozzles openings, and applied increased pumping pressure to the fluid resin to increase its velocity through those nozzle openings.
However, it is also important that resins, dyes, accelerators and other fluids be adequately mixed in with the base resin fluid stream. Merely increasing the resin fluid pressure to increase the resin spray velocity so as to maintain a thin, fanned spray flow configuration would not produce satisfactory results since the resultant fluid spray would not be adequately mixed under high fluid stream pressures. Without proper mixing of, for example, resin and catalyst fluids, the fiberglass curing rate will not be uniform. Increased fluid pressures also result in decreased pumping efficiency and higher pump operational costs and maintenance. Further, high velocity fiberglass sprays tend to "bounce" off the target and, thus, a certain amount of spray material is lost, reducing the transfer efficiency. If, as is often the case, the resin fluid is abrasive, increasing its velocity past the nozzle would also cause increased nozzle wear and necessitate frequent replacement, with the consequential down time for the entire system. As a result, it has often been found to be desirable to reduce the pump pressure on the liquid resin.
In an effort to avoid clogging of fluid streams in airless nozzles and to decrease spraying time, resin nozzles openings have also been enlarged. However, larger nozzle openings and lower operating pressures tend to reduce control over the spray flow configuration, produce more circular spray patterns, and often result in split or tail flow discontinuities in the spray pattern.
A number of prior patents have been directed to external mix resin-catalyst spray devices. U.S. Pat. Nos. 3,542,296, issued to Bradley, and 3,659,790, issued to Gelin, are representative of such patents showing fiber reinforced resin-catalyst spray apparatus. FIGS. 12 and 2, respectively, illustrate the resulting oval spray configuration. Significant flattening and uniformity in the spray flow configuration are not achieved. As a result, the transfer efficiencies of such devices is relatively low and the operating costs are increased.
Although it has been suggested, in U.S. Pat. Nos. 3,066,874, issued to Becker, and 3,507,451, issued to Johnson, that the spray flow configuration may be affected by air jets in the resin-catalyst spraying apparatus, these devices do not function to achieve the same results as the subject invention. Neither patent shows a sprayer which provides for adequate mixing of the catalyst and resin or for sufficient flattening of the spray flow. Further, these sprayers require substantially higher air jet pressures and volumes to fine tune the spray for configuration. Also, these devices are not well suited for spraying of heavy resins, such as some viscous polyesters. The Becker Patent shows the use of three independent nozzle openings for resin, catalyst, and control air. However, the control air jets of this device do not serve to flatten the spray flow. All three of these nozzle openings are arranged virtually concentricly at substantially the same location. The control air nozzle opening is generally circular and does not intersect the spray flow from opposing sides. Since the control air intersection is so close to the resin nozzle opening, substantial fine tuning of the spray flow is restricted.
The Johnson device has a complicated nozzle structure which serves a rather specific function. Air jets are provided on opposing wings spaced forwardly of the resin nozzle opening. However, these air jet openings are coincident with the catalyst nozzle opening so as to provide an aspiration force on the catalyst to draw it into the resin spray flow. As a result, independent control of catalyst atomization and spray flattening is not possible. In many circumstances, the catalyst will be excessively atomized, thus increasing the concentration of noxious fumes in the working areas, and the spray flow will be insufficiently flattened. Further, this arrangement does not provide adequate mixing of the resin and catalyst to cure properly the fiberglass on the target product. Although it has been generally suggested to employ control air jets in paint spraying apparatus to control the shape of the spray flow (Compare U.S. Pat. No. 1,990,823, issued to Gustafson, and U.S. Pat. No. 3,907,202, issued to Binoche), these paint spraying devices function differently to achieve different results with different materials, as compared to the fiberglass sprayers of the type contemplated by the present invention. The control air jets in the Gustafson and Binoche paint sprayers are shown to intersect the fluid flow fan from opposing sides at a point downstream or rebounding from the spray nozzle in attempts to flatten the spray fan. Such paint sprayers are not concerned with thorough intermixing of a plurality of reactive fluids in a primary fluid stream or with achieving an extremely smooth, flat spray with such a mixture. In fiberglass sprayers, on the other hand, proper fluid mixing can be critical. A smooth, flat resin spray flow can significantly assist resin-catalyst mixing and increase transfer efficiencies.
Further, paint sprayers are typically concerned with achieving a smooth finish on the work piece. This often requires fine atomization of the paint fluid to produce extremely small spray particles. Fiberglass sprayers typically are used for mold spraying wherein work piece finishes are determined largely by the mold surface. Thus, fine atomization of the spray mixture is not critical and, in many cases, is even undesirable as it tends to increase the concentration of harmful fumes and reduces transfer efficeincy. For these and other reasons stemming from the particular characteristics, such as lower viscosities, of paints, as opposed to fiberglass, paint sprayers generally operate at significantly higher fluid pressures, control air volumes, and spray flow velocities than hand held fiberglass sprayers.
It is therefore an object of the present invention to provide a means for flattening the configuration of a fluid spray flow and eliminating splitting of that flow in a fiberglass spraying apparatus.
Another object of the present invention is the provision of a nozzle arrangement for a fiberglass spraying system which permits low pressure atomization of a fluid mixture.
A further object of the present invention is to provide a fluid nozzle arrangement for producing a high volume, continuous linear spray flow configuration of a resin-catalyst mixture using minimal air jet and fluid pressure.
Still another object is to provide a fluid nozzle arrangement for atomizing heavy polyester resins at low fluid pressures in a two component, airless, external mix spray apparatus.
These and other objects are attained in the provision of a spray nozzle arrangement for a fiberglass spraying system having resin nozzle means, catalyst nozzle means, and control air nozzle means. The resin nozzle means includes a nozzle opening for spraying fluid resin as a resin stream. The catalyst nozzle means is spaced apart from the resin nozzle means and sprays the catalyst such that it intersects and mixes with the resin stream downstream from the resin nozzle opening. The control air nozzle means directs air flow to intersect the resin stream upstream of the mixture of the resin and catalyst. This arrangement permits the spray pattern or configuration of the resin-catalyst mixture to be controlled by controlling the low volume air flow through the flow control nozzle means so as to prevent splitting or tail formation of that flattened spray pattern and provides improved resin-catalyst mixing.
In an especially preferred embodiment of the subject invention, the catalyst nozzle means and the control air nozzle means each include a plurality of nozzle openings. At least one catalyst nozzle opening and one control air nozzle opening are disposed on each of two lateral side wings extending from and on opposite side of the resin nozzle opening. The control air rebounds off the resin nozzle to intersect the resin spray. Catalyst spray intersects the resin spray downstream from this control air intersection. In an alternative embodiment, control air intersects the material spray directly without such rebounding. In another alternative embodiment, only a single lateral side wing for catalyst is employed. Other advantageous features include the use of a pressure equalizing chamber in the liquid resin flow line upstream from the resin nozzle means to aid in low pressure atomization and flow control of that resin. Further, the three nozzle means can be contained within a unitary housing.
Since the control air intersects the resin spray flow directly, the resulting spray is more uniform. Thus, the pump pressure on the liquid resin and the velocity of the resin through the nozzle opening can be decreased with no loss of net spraying efficiency. This type of flattening of the resin spray permits much more effective fine tuning of the mixture flow. Further, auxiliary control air nozzle openings for additional shaping jets can be positioned at additional locations perpendicular to the nozzle openings for control air which define the spray flow. These auxiliary openings permit control air to alter the width of the spray flow fan as well as its thickness. By increasing the size of the nozzle opening and decreasing the resin fluid pressure in conjunction with such low volume control air, the present invention has shown, in particular embodiments, significantly improved transfer efficiencies, such as to about 80%.
Other objects, advantages, and novel features of the present invention will become apparent when the following detailed description of the preferred embodiments is considered in light of the attached drawings.